Load leveling shock absorber



July 11, 1967 J. F. SHERRILL LOAD LEVELING SHOCK ABSORBER 2 sheeis sheet1 Original Filed Nov. 8, 1963 INVENTOR. JOHN F SHERRILL ATTORNEY July11, 1967 J. F. SHERRILL LOAD LEVELING SHOCK ABSORBER Original Filed Nov.8, 1963 5 /Zfl /Z; /Z/ l? A50 5 52 0 6 v v 5 LB 9- 2 5 a l 7 5 7a WINVENTOR.

OHN E SHERRILL ATTORNEY Other objects will be apparent from UnitedStates Patent 3,330,570 LOAD LEVELIN G SHOCK ABSORBER John F. Sheri-ill,Plymouth, Ind., assignor' to Level-Aire Corporation, Toledo, Ohio, acorporation of Ohio Continuation of application Ser. No. 322,300, Nov.8, 1963. This application June 10, 1966, Ser. No. 574,842 Claims. (Cl.280-6) This invention relates to a load leveling shock absorber. Thisapplication is a continuation of my co-pending applicaton, Ser. No.322,300, filed Nov. 8, 1963, now abandoned.

Vehicles which are subject to variable loading present problems when theloading thereof is changed with respect to stability, ride smoothness,wheel contact with the road, tire wear, side sway, focus of vehicleheadlights, damage resulting from the bottoming out of a shock absorberhaving an insuflicient stroke to accommodate road shock dampening orabsorbing action, and insufficient road clearance when traveling in snowor in ruts. Various means have been utilized in devices availableheretofore to meet these problems and conditions. Thus sometimesoverload springs are mounted upon a vehicle. These are effective to meetthe overload condition but render a vehicle equipped with themuncomfortable when driven without a load. Pneumatic means have also beenutilized to provide a gas charge supplementing the springs of thevehicle as a means to produce a proper attitude and riding condition ofa loaded vehicle, but such devices usually require charging at a servicestation or other location at which an air compressor is available, andhave usually been subject to service requirements which have madeadjustment thereof to meet varying load conditions time-consuming andlaborious.

It is the primary object of this invention to provide a load levelingshock absorber which effectively overcomes the limitations anddisadvantages of prior devices and which makes possible rapid andaccurate adjustment of a vehicle to compensate for a load variation in amanner to overcome the disadvantages which normally characterize anoverloaded vehicle.

A further object is to provide a shock absorber usable upon vehiclessubject to variable loading, which is capable of rapid adjustment in asimple manner by power under fingertip control to condition itself tothe loaded condition of the vehicle for normal shock absorbingfunctioning thereof.

A further object is to provide a shock absorber with means for extendingand shortening the same at will and in a manner which does not reducethe shock dampening action thereof.

A further object is to provide a shock absorber with means for varyingthe load-carrying capacity thereof rapidly and without impairingshock-absorbing functioning thereof upon both shock loading and reboundthereof.

A further object is to provide a shock absorber including an hydraulicshock-absorbing unit, a gas charged unit cooperating with the hydraulicunit and functioning to control the length of the unit and to controlthe position of the associated vehicle and means for varying the chargeof gas applied to the gas charged unit.

the following specification. I

In the drawings:

FIG. 1 is an end view of the undercarriage of a vehicle, illustratingschematically the control for my improved load-leveling shock absorberforming a part of said carriage;

3,330,570 Patented July 11, 1967 FIG. 2 is an axial sectional detailview of one embodiment of regulating valve usable with my improved shockabsorber;

FIG. 3 is an axial sectional view illustrating another embodiment of apressure regulating valve usable with my load-leveling shock absorber;

FIG. 4 is an axial sectional view of my improved loadleveling shockabsorber construction per se;

FIG. 5 is an enlarged fragmentary axial sectional view of a valveconstruction used in the hydraulic section of my new shock absorber;

FIG. 6 is a plan view of a spring disk used in the shock absorber;

FIG. 7 is a plan view of an apertured disk used in the hydraulic valve;and

FIG. 8 is an end view of a slidable disk used in the shock absorbervalve.

Referring to the drawings which illustrate the preferred embodiment ofthe invention, the numeral 10 designates the body of a vehicle which ismounted upon suitable running gear. The running gear includes rear axle12 and wheels 14. The vehicle is provided with springs 16interconnecting the body 10 and the axle 12 in the manner wellunderstood in the art and serving to provide a yielding support of thevehicle body upon the running gear of the vehicle. Shock absorbers 18also provide an interconnection between the axle 12 and the body 10 andserve to snub or damp the action of the springs when the vehicle travelsover rough terrain.

My improved shock absorbers 18 are adapted to provide the additionalfunction of adjustment for the purpose of leveling a vehicle which issubjected to overload. For this purpose the shock absorbers 18 areconnected in a gas supply system, as illustrated schematically atFIG. 1. This gas supply system includes a charged gas container 20, suchas a conventional CO bottle Which may be charged at a pressure in theorder of 1000 pounds per square inch or any other selected pressurecharge. The container 20 will be mounted in the vehicle at anyconvenient location. A pressure regulator 22 has connection with thecharged gas container 20 for the purpose of regulating or limiting to aselected value the pressure of the gas which is discharged from thecontainer to a supply line 24. The supply line 24 has interposed thereina gas supply valve 26 which preferably is adapted for fingertipoperation and which is located in the vehicle in a convenient position,as at the dash thereof. The valve 26 is normally closed and, whenoperated, opens the supply line 24 to feed therein, and to lines 20connected to the shock absorbers 18, gas under pressure supplied fromthe container 20. The gas supply system also preferably includes apressure gauge 30 located convenient to view by the operator while hemanipulates the valve 26, and for this purpose the gauge 30 willpreferably be located at or adjacent to the dash of the vehicle. Amanually controlled bleed valve 32 is also connected to the gas supplysystem and is normally closed but is adapted to be manually opened forthe purpose of bleeding gas under pressure from the supply line 24, thegas feed line 28, and the shock absorber 18 at the will of the operator.Bleed valve 32 is preferably conveniently looated in the vehicle, as atthe dash thereof.

One form of pressure-regulating valve 22 which serves to limit thepressure at which gas is supplied from the container to the line 24 isillustrated in FIG. 2 and includes a cylindrical body 14 which has ascrew-threaded neck 36 having a screw-threaded connection in theinternally screw-threaded outlet neck 38 of the container 20.

Container has an outlet passage opening at the neck 38 and including avalve seat 40 against which a valve element 42 is normally seated by aspring 44. The regulator valve body 34 has a lateral output port 46 atits lower end, that is, the end threof adjacent the neck 36 thereof. Atits opposite end 48 the regulator body is screwthreaded to receive amanual adjusting screw 50 preferably having a knurled head. The tip ofthe screw 50 bears against a spring-adjusting disk 52 by means of whichthe compression of a coil spring 54 which in turn bears against a piston56 is controlled. Piston 56 has a circumferential seal 58, such as anO-ring, which prevents leakage of gas under high pressure past thepiston 56. The piston 56 carries an elongated plunger 60 which passeswith clearance through a central opening in the neck 36 of the regulatorbody 34 and into the outlet of the gas container 20 to bear against andunseat the valve member 42 from the valve seat 40.

This embodiment of the pressure regulator entails unseating of the valve42 at the outlet of the gas container 20 when the regulator body 34 ismounted at the outlet neck 38 of the container with the valve body neck36 screw-threaded therein. Suitable seals are provided to preventleakage between the interconnected neck portion 36 and 38. Gas underpressure from the charge in the container 20 flows past the unseatedvalve 42 and around the stem or plunger 60 to enter the regulator valvebody 34 and to flow therefrom through the outlet 46 in the supply line24. The gas in the body 34 also acts against the piston 56 to shift thesame against the action of the spring 54. When the charge of pressurecollected in .the regulator body 34 reaches a value which displaces thepiston 56 more than a predetermined extent, the plunger 60 is withdrawnfrom contact with the valve element 42 of the container 20 so that thevalve element 42 reseats and the gas container is sealed. The pressureat which this closing of the charged container from the supply lineoccurs depends upon the setting of the adjusting screw 50 and theresultant compression of the spring 54.

An alternate embodiment of a pressure regulating valve 22' isillustrated in FIG. 3. This valve has a cup-shaped valve body 62mounting a cap 64 having a central screwthreaded aperture receiving anadjusting screw 66. A piston 68 is shiftable in the body 62 and has acircumferential seal 70. A spring retainer disk 72 is engaged by theinner end of the adjusting screw 66 and bears against a coil spring 74which in turn bears against the piston 68. The closed end of thecup-shaped body 62 has an axial bore 76 formed of two differentdiameters so as to provide a valve seat or shoulder 78 intermediate itslength. A valve pin 80 is carried by the piston 68 and extends slidablythrough the reduced diameter portion of the axial body bore 76 andterminates in an enlarged valve head 82 adapted to bear against thevalve seat 78 for the purpose of sealing the axial body bore 76 at thevalve seat. A fitting 84 is screw-threaded in the outer end of the bore76 of the regulator body 62 and is threaded into the tubular neck 38 ofthe gas charged container 20. The fitting 84 includes a tubularextension 86 adapted to engage and unseat the container valve element 42and to accommodate fiow therein when said valve element is unseated. Theend of the regulator body has an outlet port 88 at which is connected anoutlet fitting 90 in turn connected with the supply line 24.

This embodiment of pressure regulator functions similarly to thatpreviously described in that the piston 68 responds to gas pressureflowing from the container 20 through the tubular extension 86, thefitting 84 and the axial bore 76 of the body of the regulator, past thevalve head 82, Gas under pressure which enters the regulator body 62discharges through the outlet port 88 and the outlet fitting 90 to theline 24, and also acts against the piston 68 to overcome the resistanceof the springs 74.

When a pressure is built up in the body 62 suflicient to compress thespring 74 to a predetermined extent, the valve head 82 seats against thevalve seat 78 and closes communication between the chamber 20 and theregulator body and thereby limits the gas pressure in the regular bodyand the supply line 24.

The shock absorbers per se are preferably of a construction asillustrated in FIG. 4. Each is formed of a hydraulic unit or componentand a gas charged unit or component. The hydraulic unit or component maybe substantially of conventional construction. The basic components ofthe hydraulic unit constitute a cylinder or housing 92 within which isslidably mounted a piston unit 94 having a piston rod 96 which extendsthrough an apertured end plate or disk 98 mounted on one end of cylinder92. An outer cylinder 100 fits with clearance around the cylinder 92 inconcentric relation thereto and has opposed end members 102 and 104fixedly mounted thereon to define a reservoir for hydraulic fluidbetween the cylinders or tubes 92 and 100 and in communication with theinterior of the tube 92. The end disk 104 has a central aperture toslidably receive the piston rod 96. The opposite end 102 of tubularmember 100 has a screw-threaded shank 106 upon which is threadedreplaceably or detachably a mounting or connector member 108, by meansof which the shock absorber 18 is connected at one end, preferably itslower end, to the vehicle, as at the axle 12.

The inner cylinder or tube 92 preferably has a centrally apertured endwall 110 in which is mounted a valve 112 normally spring-urged towardclosed position and adapted, when the parts are in assembled position,to be unseated by contact with the end 102 of the outer cylinder or tubewhich has passages therein providing communication with the reservoirspace between the inner and outer tubes 92, 100. Spacer means 114 areinterposed between the inner tube 92 and the outer tube 100 to centerthe lower free ends thereof without restraining flow of liquid in thereservoir.

One form which the valve 94 of the hydraulic unit may take isillustrated in FIGS. 4 and 5, wherein the valve construction is mountedupon the reduced screwthreaded end portion 97 of piston rod 96, whichreduced part 97 is partially screw-threaded. An apertured disk 115 bearsagainst the shoulder between the rod parts 96 and 97 and has acircumferential series of apertures 116 and a central hub portion ofincreased thickness against which bears the central portion of anapertured starshaped spring member 117 whose outer extremities arepreferably angularly bent. Disk 118 bears against the star spring 117. Asleeve 119 has a sliding fit in tubular cylinder 92 and carries at itsupper end, as seen in FIG. 5, an annular part 120 spaced therefrom bylugs 121. Annular part 120 has an annular recess defining a reducedthickness web portion 122 in which is formed one or more apertures 123having a low flow capacity compared to the apertures 116 of disk 115. Anarcuate slot 125 in disk 118 registers with the recess at which theapertures 123 are formed. An apertured disk 124 is pressed against theannular part 120 opposite that which engages the disk 118. A springfollower 126 bears against disk 124 and is pressed against by a coilspring 127 whose opposite end abuts a flange of a nut 128 threaded onthe reduced end 97 of the piston rod.

The valved piston 94 functions substantially as follows. Upon flexing ofthe vehicle springs 16 to reduce the spacing between the vehicle body 10and the axle 12 so as to move the piston rod 96 downwardly as viewed inFIGS. 4 and 5, the disk 118 is unseated from the member 119, 120 by theresistance of the liquid in the lower part of the cylinder 92 to themovement of the piston valve 94. Liquid flows through the slot 125 ofthe disk 118 and the apertures 116 of the disk 115 to enter the upperpart of the tubular cylinder 92 above the valve piston. Upon the reversemovement of the piston rod 96 and its piston 94 incident to rebound ofthe vehicle springs 16, the disk 118 reseats on part 119, 120 and flowof liquid from the upper part of the cylinder 92 through the valvepiston occurs through apertures 116 of the disk 115, slot 125 of disk118, restricted apertures 123 of part 119, 120 to apply pressure againstthe disk 124 to unseat the same against the action of the spring 127. Inthis way a snubbing of spring rebound is produced.

The end member 104 mounted on the outer cylinder 100 has a centralpassage therethrough for sliding reception of piston rod 96 therein.This aperture includes an elongated enlarged bore 130 open at. its innerface and adapted to receive a pair of O-rings 132 with a fit whichapplies a circumferential squeeze upon said O-rings. The length of theelongated enlarged bore 130 is preferably slightly less than twice thediameter of an O-ring 132. An apertured disk 134 bears against the innerface of the member 104 and against the innermost O-ring 132 andpreferably applies a slight squeeze to the two 0- rings 132 in adirection parallel to the axis of the piston rod 96. I prefer tointer-pose a coil spring 136 between the end disk 98 of the inner tube92 and the apertured disk 134. However, this is not essential and directpressure of disk 98 may be employed to hold the apertured disk 134 inits operative position pressed against the inner face of the end disk104.

The end member 104 of the outer tube 100 preferably has a skirt portion138 within which one end of the tube 100 has a sealed fit. The fitbetween tube 100 and sleeve 138 and between tube 100 and end member 102may be a drive fit and a bonding agent may be employed in conjunctionwith said drive fit to insure against leakage at the ends of the tube100. Any suitable means to provide a leak-proof connection between theinner tube 92 and the end members 98 and 110 may be provided and thispreferably will constitute a pressed fit supplemented by a bondingagent.

The gas pressure charged part of the shock absorber constructionutilizes a tubular member 140 telescoped around one end portion of thetube 100 and receiving slidably therein the end member 104 on said tube100 so as to act as a piston in the gas tube 140. The gas tube 140mounts and member 142 which has an aperture therethrough Within whichthe piston rod 96 fits and with which the piston rod 96 has fixedconnection as by a bond which provides a seal between the rod 96 and themember 142. One end portion of the tube 140 fits around a reduceddiameter portion of the member 142 and has a pressed and bonded fittherewith. Also, if desired, a sealing member 144 may extendcircumferentially to provide a seal between the member 142 and the endportion of the tube 140. The end member 142 has a screw-threaded lateralport 146 inwardly of the seal 144 and extending also through the endportion of the tube 140 so as to receive a fitting (not shown) on theend of the gas feed line 28. Suitable gasket means (not shown) may beprovided to assure a seal between the port 146 and the fitting of gasfeed line 28. The port 146 has a part 148 open at the inner face of themember 142 for delivery of gas under pressure from the feed line 28 intothe tubular member 140.

The end member 104 mounted upon the tube 100 and the skirt portion 138thereof constitutes a piston which preferably has an outer diameter witha slight clearance within the bore of the'tube 140. The opposite ends ofthis piston unit are of reduced diameter and mount thereon centeringrings 150 of slightly larger outer diameter than the piston parts 104and 138. The centering rings 150 have a snug sliding fit in the tube 140and are preferably formed of a self-lubricating synthetic material, suchas Teflon or Duralon or of any other material, such as a synthetic resinhaving properties of self-lubricity. Intermediate the entering rings theskirt 138 of the piston part 104 has a circumferential groove whichreceives a resilient annular sealing member 152, such as an O-ring. A

second circumferential groove 154 is positioned between the groovereceiving the seal ring 152 and one of the centering rings 150, and thisgroove is adapted to receive a lubricating medium, such as a lubricatinggland (not shown). The free end of the tubular member 140 whichtelescopes the tubular member carries a spacer ring 156 therein, havinga sliding and guiding fit upon the tube 100.

The free end of the piston rod 96 is screw-threaded at 160 and ispositioned externally of the end member 142. A mounting or connectormember 162 is detachably mounted upon the piston rod end 160. Themembers 162 and 108 may be of any type conventionally used in vehiclesof different constructions and manufacture for connection of a shockabsorber to a vehicle. These mounting members preferably will besupplied separately from the shock absorber per se so that mountingmembers of required character may be applied to the shock absorber atthe point of use, thus reducing the number of assemblies which must becarried in stock by a garage or service station in order to meet therequirements of vehicles of different types and manufacture requiringdifferent types of mounting means,

In the use of the device the shock absorbers per se are connected, asillustrated in FIG. 1 at 18, between the axle 12 and the body 10 of thevehicle and are connected to the gas supply system at the gas inletlines 28 thereof, which in turn are connected by lines 24 to a chargedgas tank 20, charged at high pressure and whose rate of discharge iscontrolled by the regulator 22. The device may be used for normalvehicle operation in the same manner as any hydraulic shock absorber. Inthis connection the overall length of the shock absorber, that is, thespacing between the mounting members 108 and 162 thereof, will bedetermined by the normal spacing of their connection points ascontrolled by the extent to which the vehicle springs 16 are flexedunder the weight of the vehicle body 10. The cylinders 92 and 100contain hydraulic liquid, such as oil, which is caused to flow from oneside of the piston 94 to the other incident to flexing of the springwhen the vehicle travels over rough terrain. The piston 94 serves thefunction of retarding the rate of flow of liquid therethrough uponrebound to a greater extent than it is retarded upon initial springflexure and thus accomplishes the normal shock damping, snubbing orabsorbing function of a vehicle shock absorber. Under such conditions itwill be apparent that the gas pressure charge portion of my device isinoperative.

Whenever the vehicle is overloaded to the extent that excessive flexingof the springs 16 occurs to reduce the spacing between the body 10 andthe axle 12 to an undesired extent, the gas pressure portions of theshock absorbers may be brought into play for opening the valve 16 topermit a charge of gas from the container 20 to flow through the supplylines 24 to the gas feed lines 28 and to enter the tubular cylinderportions of the shock absorbers. The gas charge introduced into thetubular cylinder portions 140 acts to supplement the vehicle bodysupporting function of the springs 116 and to elongate the shockabsorbers. This changes the attitude of the vehicle, restoring the bodyto substantially level position so that normal vehicle functioningresults. At the same time no impairment of the use of the hydraulicportion of the shock absorbers for their normal function to contract thethen increase in length incident to flexing of the springs 16 of thevehicle occurs. It will be apparent that the charge of gas in the tubecylinders 140 continues at all times to supplement thevehicle-supporting function of the springs 16. Leakage of the gas chargefrom the tubular cylinder 140 is prevented by the seals 144 and 152 andalso by the seal 130. The latter seal serves the additional function ofpreventing entry of gas under high pressure into the hydraulic unit ofthe shock absorber. Thus the integrity and functioning of the hydraulicportion of the shock absorber is insured when the shock absorbers 18 arecharged with gas at high pressure as well as at such times as the shockabsorbers contain no charge of gas at high pressure.

It will be apparent that whenever an overload condition terminates, thevehicle can be restored to normal position with its shock-snubbingaction limited to the hydraulic part of the shock absorbers by thesimple expedient of opening the bleed valve 32 to release gas underpressure from the cylinders 140. Likewise, if loading is reduced from ahigh overload condition to a medium overload condition, compensation forthe difference in the extent of overload can be had by Opening the valve32 to bleed from the cylinders 140 a part only of their charge of gas asto reduce the gas charge therein to that value required to supplementthe action of the vehicle springs 16 for the purpose of maintaining thedesired position of the vehicle body 10, that is, the desired spacing ofthe body from the rear axle 12.

While the preferred embodiment of the invention has been illustrated anddescribed, it will be understood that changes in the construction may bemade Within the scope of the appended claims without departing from thespirit of the invention.

I claim:

1. A load leveling shock absorber for a vehicle comprising a closinghydraulic unit including a cylinder, an apertured piston unitaccommodating liquid fiow therethrough at different rates in oppositedirections and a piston rod slidably projecting from said cylinder, aseal carried by said cylinder and encircling said piston rod, aconcentric circular enlargement on said cylinder adjacent the endthereof at which said rod projects, an annular seal encircling saidenlargement, a tubular member carried by the projecting part of said rodand slidably encircling said enlargement and seal, said tubular memberhaving a closed outer end, gas inlet means for supplying gas at highpressure to said tubular member, and a guide ring carried by the end ofthe telescoping portion of said tubular member and slidable on thecylinder of said hydraulic unit.

2. A load leveling shock absorber for a vehicle comprising a closedhydraulic unit including a cylinder tube, an apertured piston slidablein said tube, a reservoir tube encircling said cylinder tube withclearance and closed at one end and a piston rod projecting from saidtube, a disk sealing and projecting circumferentially from the oppositeend of each reservoir tube and having a central stepped apertureslidably receiving said rod, annular resilient sealing means seated insaid stepped disk aperture and radially squeezed therein, means forimparting a slight squeeze to said resilient sealing means parallel tosaid rod, said last named means including an apertured disk carried bysaid cylinder tube and slidably receiving said piston rod, a gaspressure tube closed at one end and carried by said piston rod, said gaspressure tube having a sliding sealed fit around said reservoir tube anddisk, and gas inlet means for supplying gas under high pressure to saidgas pressure tube.

3. A device defined in claim 2, wherein said reservoir tube sealing diskhas a circumferential groove and an annular resilient sealing ringseated in said groove.

4. A device as defined in claim 2, wherein said reservoir tube sealingdisk has a pair of spaced circumferential grooves, an annular resilientsealing ring seated in one groove, and a lubrication gland seated in theother groove.

5. A device as defined in claim 2, wherein said reservoir tube sealingdisk has a plurality of spaced circumferential areas of reduceddiameter, an annular resilient sealing ring seated at one reduceddiameter circumferential portion, and a synthetic resin guide ringseated in another reduced diameter circumferential portion and ofslightly larger diameter than said disk.

6. A load leveling shock absorber for a vehicle comprising a closedhydraulic unit including a cylinder, an apertured piston unit in saidcylinder accommodating liq- C9 uid flow therethrough at different ratesin opposite directions and a piston rod slidably projecting from saidcylinder, a seal carried by said cylinder and encircling said pistonrod, a concentric circular portion of larger diameter than said cylindermounted on said cylinder adjacent to the end thereof at which said rodprojects, an annular seal encircling said last named cylinder portion, atubular member carried by the projecting part of said rod and slidablyencircing said last named cylinder portion and last named seal, saidtubular member having a closed outer end cooperating with said hydraulicunit, circular portion and seal to define a gas-confining chamber, gasmlet means for supplying gas at high pressure to said tubular member,and guide means carried by the end of the telescoping portion of saidtubular member and slidable on the cylinder of said hydraulic unit formaintainmg said tubular member and cylinder in substantially axialalignment in all relative positions thereof.

7. A load leveling shock absorber as defined in claim 6, wherein saidlast named means constitutes guide means carried by the end portion ofsaid tubular member opposite the closed outer end thereof and slidableon the cylinder of said hydaulic unit.

8. A load leveling shock absorber as defined in claim 9, wherein saidgas inlet means includes a container charged with gas at high pressure,selectively operable means interconnecting said container and said firstcylinder to control the gas discharge in said first cylinder toselectively shift said first cylinder relative to said second cylinder,and pressure regulating means for limiting the pressure of gas suppliedto said first cylinder from said container.

9. In a shock absorber normally mounted in compressron between tworelatively shiftable anchors, comprising a first cylinder open at oneend and closed at the other end and including means at said closed endfor securing said first cylinder to one anchor, a second cylinder havingclosed ends and comprising a hydraulic fluid shock absorber having anapertured piston accommodating flow of liquid therethrough at differentrates in opposite directions and a piston rod in slidable sealedextension from one of said closed ends thereof, said second cylinder andsaid rod projecting into the open cavity of said first cylinder, saidrod being rigidly secured to said first cylinder, annular means betweenthe inner surface of said first cylinder and the outer surface of saidsecond cylinder and carried by one of said cylinders and slidablyengaged by the other cylinder for providing sliding axial movement and aseal between said first and second cylinders, said annular meanscooperating with the end of said second cylinder from which said rodextends to define a closed chamber in said first cylinder, means at theother closed end of said second cylinder for securing said secondcylinder to the other anchor, and inlet means communicating with saidclosed chamber for effecting flow of gaseous fluid into said closedchamber to establish a pressure differential between said closed chamberand atmosphere to control the spacing between said anchor securingmeans, whereby said first cylinder, said rod secured thereto and saidapertured piston are selectively movable relative to said secondcylinder in accordance with variations of the compression established bythe relative movement of said anchors and also by said pressuredifferential between said closed chamber and atmosphere.

10. A load leveling shock absorber for a vehicle having a body, arunning gear and spring suspension means, comprising an extensible andcontractible unit to interconnect said body and running gear for dampingvertical vehicle body movement incident to flexure of said springsuspension means, said unit comprising a cylindrical closed hydraulichousing, a piston slidable in said housing and having apertures thereinaccommodating flow of liquid therethrough at different rates in oppositedirections, a piston rod carried by said piston and projecting from saidhousing, sealing means carried by said housing and sealingly encirclingsaid piston rod, an enlarged concentric annular portion at the end ofsaid housing from which said rod projects, a tubular member having aclosed end carried by said rod and slidable on said annular housingportion, sealing means carried by said annular housing portion andencircled by said tubular member, means cooperating with andlongitudinally spaced from said enlarged annular housing portion forpositioning said housing and tubular member substantially in axialalignment in all relative positions thereof, said positioning meansbeing carried by one of said housing portion and tubular member andengaged by the other, said housing, annular enlargement and sealingmeans defining a sealing closure slidable in said tubular member todefine a sealed gas chamber therein, and gas intake means carried bysaid tubular member in communication with said chamber.

References Cited UNITED STATES PATENTS Downer.

Koenig 137-50542 Sorensen 137-50542 X Schmitz.

Spears 137-50542 X Schultze.

Broadwell.

Long 267-64 X Australia.

15 BENJAMIN HERSH, Primary Examiner.

P. GOODMAN, Assistant Examiner.

1. A LOAD LEVELING SHOCK ABSORBER FOR A VEHICLE COMPRISING A CLOSINGHYDRAULIC UNIT INCLUDING A CYLINDER, AN APERTURED PISTON UNITACCOMMODATING LIQUID FLOW THERETHROUGH AT DIFFERENT RATES IN OPPOSITEDIRECTIONS AND A PISTON ROD SLIDABLY PROJECTING FROM SAID CYLINDER, ASEAL CARRIED BY SAID CYLINDER AND ENCIRCLING SAID PISTON ROD, ACONCENTRIC CIRCULAR ENLARGEMENT ON SAID CYLINDER ADJACENT THE ENDTHEREOF AT WHICH SAID ROD PROJECTS, AN ANNULAR SEAL ENCIRCLING SAIDENLARGEMENT, A TUBULAR MEMBER CARRIED BY THE PROJECTING PART OF SAID RODAND SLIDABLY ENCIRCLING SAID ENLARGEMENT AND SEAL, SAID TUBULAR MEMBERHAVING A CLOSED OUTER END, GAS INLET MEANS FOR SUPPLYING GAS AT HIGHPRESSURE TO SAID TUBULAR MEMBER, AND A GUIDE RING CARRIED BY THE END OFTHE TELESCOPING PORTION OF SAID TUBULAR MEMBER AND SLIDABLE ON THECYLINDER OF SAID HYDRAULIC UNIT.